System of frequency or speed measurement and control



March 25, 1930. F. wuNscH 1,751,538

SYSTEM OF FREQUENCY OR SPEED MEASUREMENT AND CONTROL Filed March 27,1925 2 Sheets-Sheet l 2& 21 19 ,5 fi\.4e 1 6 INVENTOR.

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:4 A TTORNE Y.

March 25, 1930. F. WUNSCH 1,751,538

SYSTEM OF FREQUENCY OR SPEED MEASUREMENT AND CONTROL Filed March 27,1925 2 Sheets-Sheet 2 INVENTOR.

fay/WW4 Max-63%? ATTORNEY.

Patented Mar. 25, 1930 I or PHILADELPHIA, nor comm, or PHILADELPHIA,

PENNSYLVANIA, ASSIGNOR T LEEDS & N ORTH- PENNSYLVANIA, A CORPORATION OFPENNSYL- BYSTEM OI FREQUENCY 0R SPEED MEASURIMEN T AND CONTROLApplication filed March 27, 1925. Serial No. 18,794.

. My invention relates to asystem formeasurng or recording the frequencyof a fluctuatmg or alternating current or the speed of a moving system.

In accordance with my invention, there is utilized a Wheatstone bridgewith which is employed an alternating current galvanometer and whosearms comprise impedances (which term includes non-inductive resistancesand reactances, either capacitat-ive or inductive), with means for sovaryingor adj usting the relative magnitudes of the impedances in thebridge arms of each of two pairs I of bridge arms to effect a balancefor each of various frequencies by effecting equality be tween threeratios, such as the ratio of the resistance components of the impedancesof two arms, the ratio of the reactance components of the impedances oftwo arms, and the ratio of the impedances of two other arms, wherebyvariation of relation between the phases of the galvanometer fieldcurrent and of the current in the bridge is avoided.

More particular] in accordance with my invention, and pre erably, thereare utilized in a bridge arm a condenser with a resistance in shuntthereto, and in another arm a condenser and a resistance in seriestherewith, and in the remaining arms resistances, with slide wire oradjustable resistances between the arms of each pair ofv arms foreffecting for each of various frequencies the aforesai equality of threeratios.

Further in accordance with my invention,

' there is provided in association with the movable structure eifectingthe adjustment of the slide wire or adjustable resistances a scale andpointer for directly reading frequencies, speeds or equivalents thereto.

Further in accordance with my invention, the galvanometer of theWheatstone bridge controls a moving system or movable structure servingto rebalance the bridge, and also to produce a record of frequency orspeed variation.

My invention resides in a method and apparatus of the characterhereinafter described and claimed.

For an understanding of my method, and for an illustration of some ofthe various tact 3. In the apparatus may take, to the accompanying formsmy be had which: Fig. 1 is a diagrammatic view of apparatus suita le forpracticing my method and embodying my invention in one of its forms; andFig. l is a modification.

Fig. 2 is a fragmentary perspective view of recording and controlmechanism utilizable in accordance with my invention.

Fig. 3 is a diagrammatic view of a system for controlling speed orfrequency.

igs. 4c and 5 are fragmentary views of modified forms of speed orfrequency-controlling means.

eferring to Fig. 1, A is a generator or source of alternating orfluctuatin current whose frequency is to be measure or indicated. Itsterminals are connected, respectively, to the conjugate terminals orpoints 1 and 2 of a Wheatstone bridge whose other conjugate points areat the points of engagement of the contacts 3 and 4 movable alon theslide wires or adjustable resistances and S respectively. In the firstbridge arm is included a condenser G, shunted by the non-inductiveresistance 7', in series with that ortion 1" of the non-inductiveresistance lying to the left of the consecond bridge arm are incondenserC non-inductive rereference is to drawings, in

cluded the sistance 1- a constituting the remainder of the resistance Sto the right of the contact 3. In the third bridge arm are included thenon-inductive resistance r and the portion 7' of the slide wireresistance S to the right of the contact 4. In the fourth bridge arm arethe resistance a constituting the remainder of the resistance S to theleft of the contact 4, and the non-inductive resistance r".

In case the resistances S and S, which may be in the form of simplewires or in the form of helices along which the contacts? and 4 move,are not by themselves of exactly correct values, they ma as wellunderstood in the art of slide wires, be shunted by resistances such as7* and 7", respectively, to ensure between-their terminals exactly thecorresistance.

rect or desired amount of and the non-inductive resistance It isdesirable that all of the resistances tious or equivalent alternatingcurrent reaforementioned shall have small or substansistance which,however, changes in magnitially zero temperature co-eflicient, to avoidtude with changes in frequency, and corn influence of temperature uponthe measureprises not only the resistances 7, 1*, but, in adr ditionztheapparent fietitious esistance 70 confugatfi (50noifrespondifig initht losses;

between. condenser C per se, and of the combination the contacts 3. and4, is connec movable of the condenserf Qyvith 1 ng istr. I I

1' i-ng ipointef ori nee'dle-i-95L-=The coil wiiidingspends W f t I may,as Well understood in the art, be r and the apparent or fictitioushunted y a s nce 539 itah emesas riablw th ir eueeeyedeete. losses ofnitude. Th alternatiifig ma-gm 1c lieltlof the the do denser CQif any;HO'WeVer, When the galvanometer is produced by c urren t;jri-ro ncondenser grade mica condenser, 15 the source A traversing theg'aly'anorneter with low loss, We may Wr te 80 elcl.=, .i ;l @i lga fi$0 .1; mscries withwhich L ma-ybeeconnectedg th e I f The ahasaangle ofthe current exciting li enometer lclrmaghetswiudi g f .:Zi il hillfifisfifi tgh i i pforee m y. cha se causes, such, in

i t o. lessmeansar pr ruled, I ,;.truerbalance-.o hebridg, egarclless-of th shifting o iphase of the fieldsexciti'ngiclirrent. 157 of thegalvanometer. To this-end? v 1:111 thief 1,. t reearatios shall be'equaliztor all SP Q Y 'yaf hi flPlQ UE -Q within the' rangezt'be-measured and ire-and 1 are; rthernl gmtuileseof i istanccsm-rEquations (Hz-and t inathe 'elLk-no Qi l z ii gmurlbl Edeterminabletheapro1ier value isrc stances fend capacities.

an arrangement such as; indicated: :in 1 -z :-for; ineasuri;ngwdesiredrange ofifrequencies, I

ucee or 'ngthe measurenients unmakapossiblei' a lngeunderstooclthat'i-the contactsi3'andEli- 1 noved i'irun-ison-i-ivith each:other'b'ecame attached: to-atlieisame aniorablmmeinberi' arr Ifiii'Dgsilie pointer cluandecoeacting zavithathe =isfiationaryjsca le0-:calibrated;in termsirifaire- I :queney', speed or'both,or;anyequivalent .of iio 1,them.. The c-ontacts' 3 anglatak'eaiid-iifi'ereiit .rposrtromforeach .cl-lfierentfrequencyynr orderto balance the bridgeafiirtthat reqrrerfeyg' 'in which :e'rent'athc'galvanoin'ete zcoil QO in a its:zer.oi: "E'horiedeflctingpositionr x; 1

1: i-From the-forego-ri i g", l;

fcha nge the ratiomf the resistances: v 7

third and fourth a'rnis fith'c bridg ejin pro ,p'ortion to--thcfchangean h'c rat i'o o jthe ef zfe ctizve'resistance 1n re' a and secoiidarlns o n order hat 1th equality-of?ratios-entire 'ri n' Equation .69.55%- which ;l. ly-:; bEJQZS: truly balanced regardless ofchangesoffthe n n the= bile th tud iari ch ngesin eter' field fi; d glii fifQr saiclavree Vhile measurement of freque istan e 1, "n t he;ac uliz on inductire described "in eoni'i'ectioii'=with nitude proportionalto frequency may similarly be measured. For example, the speed of arotating member may be measured by driving an alternating currentgenerator, as

q A, by such member, and then measuring the frequency of the currentdelivered by the generator. I

It shall be understood that my invention includes equivalents of thearrangement shown in Fig. 1, for it will be understood that in lieu ofor with resistances r and 9" may be utilized either inductive orcapacitative reactances, and that the slide wire S may represent aninductive reactance, variable portions of which are included in theneighboring bridge arms, or may represent complementarily variablecapacities included in the neighboring bridge arms. Furthermore, it willbe understood that in the first and secand bridge arms there may be usedinductive reactances, and that the slide wire S may be inductive, or maybe complementarily variable capacities connected in the neighboringridge arms.

In Fig. 1 is shown such a generally equivalent arrangement in which inthe first bridge arm are the serially relate-d inductance L andresistance r, and in the second bridge arm the inductance L shunted by aresistance r. it will be understood that the total resistance of thefirst arm of the bridge comprises the resistance r", the resistance ofthe conductor of the inductance L, and the resistance T, which last ispresent as a separate unit if the resistance of the conductor of theinductance L is not itself sufficient.

in this case again Equation (1) applies. .7 and d are the resistance andreactance components of one arm of the bridge, as for example, the firstarm including L, 1'", 7'; r and (Z are respectively the resistance andreactance components of another arm of the bridge, for example thesecond arm including r r, r and L and a and b are, respectively theresistances or impedances of the other arms of the bridge, for examplethe third and fourth arms including respectively 7*, r and r 7"".

r resistance of inductance L trol mechanism, one example of which isillustrated in Fig. 2, and corresponding with a structure of thecharacter disclosed in prior Letters Patent of the United States toLeeds No. 1,125,699, January 19, 1915.

Referring to Fig. 2, M is an electric motor or other suitable source ofpower rotating the shaft 5 at substantially constant speed. A lever 6 ispivoted at its upper end on a horizontal axis and has pivoted thereto ona horizontal axis at its lower end the arm 7, on each end of which is ashoe 7, of cork or the like, frictionally engaging the rim 8 of theclutch disk or wheel 9, secured upon the shaft 10 of the movablestructure or system. 'Secured upon the shaft 5 is a cam 11, whichperiodically engages the lever 6 and moves it outwardly, in oppositionto a spring, not shown, thereby lifting the shoes 7* from the rim 8, thespring returning the shoes into engagement with the rim afterpredetermined rotation of the cam 11. Upon the shaft 5 is secured asecond cam 12, which, after the shoes 7 a have been lifted from the rimby the cam 11, actuates the finger 13 on the lower end of the arm 14secured at its upper end to the member 15 pivoted on a horizontal axisat 16. Upon the member 15 is secured the member 17, whose upper edge 18is inclined outwardly from the center. Disposed immediately above theedge 18 is the aforesaid needle or pointer 19 of the alternatin currentgalvanometer whose coil is 20. t the opposite ends of the member 17 arethe abutments 21 for limiting the deflection of the needle 19. Directlyabove the needle 19 and beneath which it normally freely swings are theedges 22, preferably straight and horizontal, upon the members 23, 23pivoted at 24, 2 1, and extending toward each other, leaving a gap ofsuilicient width between their inner ends for free entry of the needle19 when in balanced or zero position, corresponding with a balance ofthe VVheatstone bridge of the character shown in Figs. 1 and 3. Theneedle 19 normally swings freely between the edge 18 .and the members23, 23, which latter have downwardly extendin arms 25, 25, biased towardeach other by the spring 26. Attached to the lower end of the arm orlever 6 is a triangular plate 27 carrying the pins 28, 28, co-operatingwith the lower ends of the members 25, 25. At opposite ends of the arm 7are the lugs 29, 29, adapted to be engaged by the cams 30, 80, similarin shape and similarly positioned and secured upon the shaft 5 As thegalvanometer needle 19 deflects in the one direction or the other, theshaft 10 will be rotated in the one direction or the other, and to anextent corresponding to the extent of the galvanometer deflection. Forexample, when the needle 19 deflects to the right, Fig. 2, due toperiodic vertical movement of member 15 by cam 12, the needle 19 isclamped the inclinededge 18 and .wise direction about its and sotilting-t lower edge 22 of the: rigllt hand member 23 causin the M11125to tiltedin a clockivot 24, thereby pushingthe. ri ht hand n 28 on plate27,

e movabl or driving clutch f'or arm 6 in aiclockwise direction while camrim 8 of wheel 9 and soon thereafter the left hand cam 30 engages thecar 29, which has 0 been elevated, pushing it downwardly due to rotationof shaft 5, to restore it to the horizontal position indicated, but inso moving carrying the arcuate contacts 33 and 34 back to normalposition the clutch member rotates the. disk 9 and shaft 10 afiixedthereto in a counter-clockwise direction.

Secured upon the shaft 10 is a disk 31 of insulating material, carryingupon its periphery the aforesaid resistances or impedances S, S, whichin this example, as indicated in Fig. 3, are rotated, while theircoacting contacts 3 and 4 are stationary. Secured upon the shaft 10 is asecond disk 32 with which co-acts the stationary contact or The disks 31and 32 are adjustable to any suitable angles with respect to each otherand with respect to thesha-ft 1O bysuitable set screws 36 and 37.

Secured upon the shaft 10 is the grooved pulley wheel 38, around whichis wrapped the cord 39, which passes over the idler rollers 40 and hasattached thereto the pen .or marker 41 for drawing upon the record sheetor paper 42 a mark or record 43 ofthe changes of frequency or speed. Thepaper 42 is driven by the motor M, as we llv understood in the art. Disk31 may carry the frequency or speed scale 6 co-acting with stationarypointer d.

Referring to Fig. 3, the movable structure or system of Fig. 2 is shownin so far as it comprises the shaft 10 and the disks 31 and 32. Theslide wires S, S are comprehended in a Wheatstone bridge of thecharacter indicated in Fig. 1.

A turbine or other source of power, or generically a rotating system, T,drives the alternating current generator or source A related to thebridge of Fig. 3 as the source A is related to the bridge in Fig. 1. The

' source A in this instance may be a small alternating current generatordriven by the rotary structure T through the shaft 44 for purposesmerely of measuring or controlling the speed of-the device T. Or it maybe an alternating current generator of large capacity for supplyingcurrent to any suitable load connected to the supply circuit conductors45 and 46, in which case the frequency or speed of T and A may becontrolled by con- M receiving brush trolling the opening of the valve Vcontrolling the rate of supply of motive fluid or steam through the pipe47 to the turbine T. In this case the brush 35 with contacts 33 and 34control the reversible electric motor current from any suitable source,as 48. When the disk 32 is in,the

is deenergized, and this condition corresponds with balance of the\Vheatstone bridge for balanced, causing a deflection of thegalvaposition indicated in Fig. 3, the motor M nometer and its needle19, causing in turn a rotation of the shaft 10 to an extentcorresponding with the extent of unbalance of the bridge, and in suchdirection that the contact 33, for example, will be brought intoengagement with. the contact, 35, energizing the motor M which runs in acertain direction, rotating the shaft 49, through any suitable greatgear reduction, generically represented by the pulleys 50, 51 and belt52, thereby causing the member 53 to advance upwardly along the threadedshaft 49, carrying the abutment 54 upwardly, with resultant tendency tocompress the spring 55, which opposes'the fly ball governor 56, drivenby the turbine or device T, to partially close the valve V, causingreduction in speed and frequency. Similarly, when the frequency or speeddiminishes, the motor M will be energized through contacts 34 and 35,and will rotate in the opposite direction, and effect an increase in theopening of the valve V, with resultant increased speed and frequency. Inboth cases the speed or frequency is varied or changed toward thedesired frequency, at which the contact 35 is in engagement with neitherof the contacts 33 and 34, and the bridge is in balance. When thefrequency or speed changes from the desired magnitude, the lVheatstonebridge is unbalanced, the galvanometer deflects, and the disks 31 and 32are rotated by'the shaft 10 in a direction tending to balance the bridgeand cause a change in the speed or frequency back toward the desiredmagnitude, and when this condition is reached or obtains the bridge isin balance and the motor M is deenergized.

The governor 56, or its equivalent, at a given setting, or position ofabutment 54, is effective of itself to maintain the speed of the systemor frequency of the alternator with a range of variation broader than issuitable or desirable. In the arrangement described, by modifyingautomatically in accordance with change of frequency the acsubstantiallyconstant, less than of 1% variation being obtained in actual practice.

At the same time, -the automatic system produces a record of the speedor frequency upon the record paper 42, or indicates speed or frequencyby scale 6 on disk 31.

In lieu of the valve control mechanism indicated in'Fig. ,3, there maybe utilized that indicatedin Fig. 4, where through suitable reducinggearing, the motor M rotates the valve stem to effect partial closure oropening of the valve V upon increase or decrease of speed or frequency.In either of the valve arrangements of Figs. 3 and 4, it will beunderstood that the valve may be either in the main steam or motivefluid line, or may be in a by-pass, and that the governor 56 of Fig. 3may be either the main overnor or an auxiliary governor of the tur ineT.

In Fig. 5 there is fragmentarily indicated an alternating currentgenerator or source A, either solely for speed measurement, or forsupplying current to a consumption circuit, as in Fig. 3. In this case,however, the turbine T is replaced by an electric motor M", such, forexample, as a shunt motor, the armature 57 and shunt field 58, with avariable resistance 59 in the armature circuit, or in the field circuitif desired, and adjusted by the contact 60 moved by the nut 61 movablealong the threaded shaft 62 driven through suitable reduction gearing bythe reversible motor M of Fig. 3.

In the operation of a frequency or speed control system of the characterhereinbefore described and claimed in divisional application Serial No.288,688, filed June 27, 1928,

the frequency of an alternating or fluctuating current is in effectdetermined or measured, as in the case of Figs. 1 and 1, or equivalent,and in addition, a frequency or speed control is effected.

It will further be understood that my invention is not limited to themeasurement of frequencies of 25, 60 or more cycles per second ascommonly utilized on power and lighting circuits, but comprehends alsothe measurement of higher frequencies, including the so-called high orradio frequencies.

For brevity in the appended claims, the term frequency is employed in ageneric sense to include frequency, speed, or equivalent magnitudeproportional to or dependent upon frequency or speed.

What I claim is:

1. The method of measuring frequency by a IVheatstone bridgehavingcombinations of resistance and reactance in different bridge arms, whichcomprises effecting balance of the bridge by varyingthe relativemagnitudes of impedances in the bridge arms to effect equality betweenthe ratio of the re sistance components of two arms of the bridge, theratio of the reactance components of said arms of the bridge, and theratio of the impedances of the other arms of the bridge.

having 2. Apparatus for measuring frequency comprising a Wheatstonebridge, a conjugate conductor of said bridge including a source offluctuating current, a fluctuating current galvanometer connected in theother conjugate conductor of said bridge, means for energizing the fieldof said galvanometer from said source, combinations of resistance andreactance in certain arms of said bridge, impedances in the other armsof said bridge, means for adjusting the relation of the magnitudes ofthe impedances in said first named arms of said bridge, and means forcomplementarily adjusting the relation of the magnitudes of theimpedances in said other arms of said bridge for effecting equalitybetween the ratio of the resistance components of said first named armsof said bridge, the ratio of the reactance components of said firstnamed arms of said bridge, and the ratio of the impedances of said otherarms of said bridge.

3. Apparatus for measuring frequency comprising a IVheatstone bridge, aconjugate conductor of said bridge including a source of fluctuatingcurrent, a fluctuating current galvanometer connected in the otherconjugate conductor of said bridge, means for energizing the field ofsaid galvanometer from said source, combinations of resistance andreactance in arms of said bridge, impedances in the other arms of saidbridge, members constituting the terminals of said second conjugateconductor movable in unison for varying the relative magnitude of theimpedances in said first named arms and for complementarily varying therelative magnitude of the impedances in said other arms of said bridgeto effect equality between the ratio of the resistance components ofsaid first named arms of said bridge, the ratio of the reactancecomponents of said first named arms of said bridge, and the ratio of theimpedances of said other arms of said bridge, and relatively movablescale and pointer members one of which is movable with said members.

4. Apparatus for measuring frequency comprising a Wheatstone bridge, aconjugate conductor of said bridge including a source of fluctuatingcurrent, a fluctuating current galvanometer connected in the otherconjugate conductor of said bridge, means for energizing the field ofsaid galvanometer from said source, a condenser and resistance inarallel with each other in one arm of said liridge, a condenser andresistance in series with each other in a second arm of said bridge, aslide wire connecting said arms, impedances in the other arms of saidbridge, a second slide wire connecting said other arms, contactsconstituting the terminals of said second named conjugate conductor coacting with said slide wires for effecting balance of said bridge byeffecting equality between the ratio of the resistance components ofsaid first and second named arms of said of fluctuating current, afluctuating currentgalvanometer connected in the other conjugateconductor of said bridge, means for energizing the field of saidgalvanometer from said source, a condenser and resistance in parallelwith each other in one arm of said bridge, a condenser and resistance inseries with each other in a second arm of said bridge, a slide wireconnecting said arms,

' impedances in the other arms of said bridge,

which is movable in unison a second slide wire connecting said otherarms, contacts constituting the terminals of said second named conjugateconductor coacting with said slide wires for effecting bal an ce of saidbridge by effecting equality be tween the ratio of the resistancecomponents of said first and second named arms of said bridge, the ratioof the reactance components of said first and second named arms of saidbridge,'and the ratio of the impedance of said other arms of saidbridge, means efiecting movement ofsaid contacts in unison with eachother, and scale and pointer members movable relatively to each otherand one of with said contacts.

6. The combination with a Wheatstone bridge, of a source of fluctuatingcurrent in a conjugate conductor thereof, a fluctuating currentgalvanometer in the other conjugate conductor of said bridge, means forexciting said galvanometer from said source, a reactance and resistancein parallel therewith in one arm of said bridge, a reactance andresistance in series therewith in a second arm of said bridge, anlmpedance connect-1n said arms and co-actlng with a, terminal 0 saidsecond named conjugate conductor, impedances in the other arms of saidbridge, and an impedance connecting said other arm and co-acting withthe other terminal of said second named conjugate conductor efl'ecting asupplementary adjustment for effecting true balance of said bridgewithout effect by shifting of phase of the current in saidgalvanometer-exciting means.

7. In combination, a Wheatstone bridge having combinations ofreactanceand resistance in diflierent bridge arms, impedances in the other bridgearms, a source of fluctuating current in a conjugate conductor of saidbridge, a fluctuating current galvanolneter in the other conjugateconductor of said bridge, means for exciting the galvanometer field fromsaid source, movable structure controlled by said galvanometer when saidbridge is unbalanced, means controlled by said movable structure foreffecting balance of said of said first-named means,

I e fi'ect-equality between-the ratio of the resistance components ofsaid first named'arms,

the ratio of the reactance components of said ratio of the 1m firstnamed arms, and the pedances of said other arms.

8. The method of measuring frequency which comprises impressing aflunctuating current upon an electrical network balanced at apredeterminedfrequency, balancing the network at the fre uency of theimpressed current by varying the ma itude and distribution of impedanceinclu ed in the network, and determining from the magnitude of saidvariation of impedance the difference between the impressed andredetermined frequencies.

9. Apparatus comprising an electrical network a source of fluctuatingcurrent connected thereto, means indicating -balanced condition of saidnetwork, structure movable to efl'ect balance of said network at thefrequency of said fluctuating current, and means associated with saidmovable structure to indicate the frequency at which said network isbalanced.

10. In a system of the character described, means having a certainfrequency, adjustable means having a neutral position and responsive todiflerent conditions of frequency, means providing an operatinconnection between said first and secon -named means such as to bringsaid second-named means under the influence of said certain frequencyable when saidsecond-named means is under such influence to effect adustment thereof in such wise as to cause the same to assume said neutralposition.

FELIX WUNSOH.

0r measurin fre uenc g and means oper-

